The present invention relates to ceramic greenware, particularly greenware which can be fired into abrasive articles.
Abrasive articles such as sharpening stones, honing stones, mold stones, dressing sticks, grinding wheels, and microfinishing stones are useful in polishing, sharpening, dressing, shaping and the like. For example, an Arkansas stone can be used to sharpen knives Arkansas stones can be prepared synthetically, or, as indicated by the name, can be cut from natural stone. Synthetic Arkansas stones and other synthetic abrasive articles are prepared by firing the appropriate greenware. The greenware is prepared by cold pressing a mixture comprising abrasive particles, a temporary binder and vitreous bond components. Without the binder the greenware would lose its shape or fall apart upon removal from the cold pressing mold. The strength of the greenware, i.e. green strength, needs to be high enough to prevent damage to the greenware during firing and handling. For example, during transfer from the press to the firing furnace greenware of insufficient strength can be deformed resulting in, e.g. chipped edges or finger marks.
Following cold pressing, the greenware is fired. The purpose of firing is to decompose the binder and melt the vitreous bond component of the greenware. A binder commonly employed in the abrasive industry is dextrin. This dextrin is added to the pregreenware batch as a fine powder and is mixed with the abrasive grit and bond components. When making small articles using what is referred to as "press to size" technology it is common to use large amounts of dextrin. This is especially true for fine grain (e.g. 400 grit) materials with high (e.g. 10) grit to bond ratios. This large amount of dextrin is required to provide sufficient green strength. Large amounts of dextrin require long burn off times to ensure complete removal of the dextrin. Incomplete removal of dextrin leaves carbonaceous residue in the greenware. This residue leads to bubbles and imperfections, such as bloating, upon firing.
In view of the disadvantages associated with dextrin, it would be advantageous to have a readily removable temporary binder for abrasive greenware. It also would be advantageous if this binder could be employed in lower amounts than dextrin to give equal or greater green strength, and if it could be used with shorter binder burn out cycles, thereby improving productivity.